This invention is in the field of protectors for sensitive optical detectors against high-power or high-intensity radiation. Such protectors are also known as optical power limiters and take many forms, such as mechanical or electro-optic shutters, plasma devices, bleachable filters, exploding or fusing mirrors, interference filters (for lasers), and nonlinear optical materials in various configurations. Optical phenomena such as blocking, absorbing, reflecting, scattering, and defocusing are used to advantage in such limiters. Whereas most of the known limiters are for protection against visible light, the instant invention is usable with visible, ultraviolet, or infrared radiation using various materials which exhibit two-photon absorption. One of the materials capable of two-photon absorption of infrared radiation used in this invention is the same as that used by the present inventors and others in U.S. patent application Ser. No. 07/213873, filed June 30, 1988.